The invention concerns a composite material strip for producing an electric component, in particular a resistor, such as for example a low-resistance current-measuring resistor (“shunt”). Furthermore, the invention concerns a corresponding production method and a corresponding electric component.
EP 0 605 800 A1 discloses a low-resistance current-measuring resistor which consists of two plate-shaped connecting parts made of a conductor material (e.g. copper) and an equally plate-shaped resistance element inserted between them and made of a resistance material (e.g. Manganin®). This known current-measuring resistor may be produced economically from a composite material strip which consists of three material strips welded along a longitudinal seam. The two outer material strips here consist of a conductor material (e.g. copper), while the middle material strip consists of the resistance material (e.g. Manganin®). The individual current-measuring resistors may be punched out of the composite material strip transversely to the strip longitudinal direction. It should be stated here that the individual material strips of the composite material strip are connected together by means of electron beam welding. This is easily possible because the resistance material (e.g. Manganin®) on the one hand and the conductor material (e.g. copper) on the other hand can be welded together easily.
In some applications, however, there is a technical need to configure the current-measuring resistor with an aluminum connecting part on one side. This is not possible with electron beam welding, since aluminum on one side and copper or Manganin® on the other cannot be welded together or are difficult to weld together. Thus in all thermal welding processes (e.g. WIG welding (WIG: Wolfram Inert Gas), laser welding, electron beam welding etc.), an intermetallic phase is formed between the aluminum and copper, wherein this intermetallic phase is extremely brittle. The brittleness of the weld seam in turn leads to a low strength, so this method is not suitable for industrial applications.
Cold welding processes (e.g. friction welding) indeed prevent the occurrence of this disruptive intermetallic connection between the aluminum component and the copper component. However, these welding processes are not suitable for producing a multilayer composite material strip. Known friction welding usually only functions on a single piece, and is therefore relatively labor-intensive and costly.
The connection to an aluminum component is useful for example in hybrid and electric vehicles which are operated with a comparatively high steady current, so that the conductor rails must have a significantly larger cross-section than in conventional vehicles with an internal combustion engine. The same however also applies to all other modern motor vehicles, since more and more functions are being implemented via electric actuators (valves, motors), whereby the mean steady current in larger vehicles is already approaching 200 A. For reasons of weight and cost therefore, conductor rails are being increasingly made of aluminum. Both on the ground side and on the live side (battery or alternator) however, a transition must be made between the aluminum conductor rail and the components which are usually made of copper.
DE 10 2012 006 641 A1 discloses a cable-connecting element in which an insert of aluminum is plated onto a flat part made of copper. The copper part and the aluminum part are here arranged planar parallel to each other, which excludes production from a composite material strip.
The same applies to U.S. Pat. No. 3,895,851. This publication discloses a cable-connecting element in which an aluminum coating is applied to a copper part. This structure also excludes production from a composite material strip.
In U.S. Pat. No. 3,157,735 and DE 10 2004 009 651 A1 too, the aluminum part and the copper part are arranged planar parallel to each other, which excludes production from a composite material strip.
Furthermore, reference is made to DE 42 43 349 A1 and DE 10 2012 013 036 A1 as the prior art.
The invention is therefore based on the object of achieving such a transition from an aluminum component to a copper component.
This object is achieved by a composite material strip, a production method and a corresponding component of the invention.